Ethylene copolymers are inexpensive and have excellent molding properties, and also have excellent physical properties such as transparency, strength and the like. Therefore, the ethylene copolymers are practically used in a wide field.
However, the weatherability of ethylene copolymers is not always sufficient, and as a result, the ethylene copolymers have the restriction in the outdoor use where they are exposed to direct sunlight. A method of adding additives such as benzophenone-based UV absorbers, benzotriazole-based UV absorbers, hindered amine-based photostabilizers or the like is conventional as a method for improving the weatherability of ethylene copolymers. However, the improvement effect is not sufficient due to bleed out of additives. The tendency of this bleed out is particularly remarkable in a product of a thin thickness such as a film. It is proposed to minimize the bleed out by increasing the molecular weight of additives.
For example, Japanese Patent Application (OPI) Nos. 126240/76 and 137358/82 disclose this proposal (the term "OPI" as used herein refers to "published unexamined Japanese patent application"). The effect by the increase of molecular weight of additives can be expected from the standpoint of the bleed out property. However, in the case of adding to non-polar solvents such as polyethylene, dispersibility of additives is not sufficient and a sufficient effect cannot be always exhibited.